1. Field of the Invention
This invention relates to cameras, and more particularly to cameras capble of altering the size of the area of the picture frame.
2. Description of the Related Art
A camera using roll film of 35 mm wide which is able to take negatives in a picture frame of the 24 mm.times.25 mm is generally called a "35 mm" or "full-size" camera. There is also a well known "half-size" camera whose picture frame, although using roll film of the same size, is sized to 24 mm.times.17.5 mm.
In the past, the non-interchange-lens type of full-size camera (or compact camera) and the half-size camera were manufactured as thoroughly independent articles of each other. Therefore, the camera user who wanted to make photographs of the full-size and half-size formats was obliged to carry both the full-size and half-size cameras.
On this account, to obviate such trouble, a camera capable of shooting both the full-size and half-size formats selectively was not available in the market. There has also been previous proposals for imparting into such a changeable format camera, a capability of selectively setting two viewfinder frames for both the full-size and half-size formats in automatic response to a changeover between these formats, as, for example, in Japanese Patent Publication No. Sho 60-57577.
In the ever sold camera of the type described, however, no automatic means was provided for adjusting the size of the area of the viewfinder frame in accordance with the altered size of the area of the picture frame. After he had changed the picture frame from the full size to the half size, the photographer, before shooting, often forgot to set the viewfinder frame off for the half-size format. As a result, there was a drawback that a high percentage of the photographs taken which would be different in composition from what the photographer intended to make was high.
According to the above-mentioned proposal for a camera in which the viewfinder frame size is changed in automatic response to a change of the picture frame size, on the other hand, there is no possibility of erroneous framing when taking shots after the picture frame has been changed from the full size to the half size But, to rely only on this proposal is makes it difficult for the 2-format changeover type camera to attain its full usefulness.
To realize a changeable format camera of high usefulness, the following factors must generally be taken into account in its design. But, prior known cameras by the aforesaid proposal are not designed as such
The employment of the capability of changing over the picture frame between two sizes in the camera whose photographic lens and finder have no common optical path makes troublesome the parallax adjustment when the camera is manufactured. The aforesaid proposal, has, however, been applied to this camera ignoring such a problem.
For the coexistence of frames of different size in one roll film, the film developing laboratory system up to the present time cannot cope yet with such a film in the automatic printing treatment and others. It will, therefore, very much hamper such treatment. This situation is not considered in the aforesaid proposal.
The impartment of the format changeability into the camera produces a problem that the adjacent two frames of different size are caused to partly overlap each other as with the change of the picture frame from the half to the full size. The camera of the aforesaid proposal is not provided with means for eliminating that problem.
When shooting frames of smaller or half size, the image sharpness becomes more susceptible to camera-shake than when shooting frames of larger or full size. The prior known cameras suffer this problem.